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    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>
        /**
 * 把平铺的数组结构转成树形结构
 */
          const arr =   [
            { 'id': '29', 'pid': '',     'name': '总裁办' },
            { 'id': '2c', 'pid': '',     'name': '财务部' },
            { 'id': 'd2', 'pid': '',     'name': '技术部'},
            { 'id': '2d', 'pid': '2c', 'name': '财务核算部'},
            { 'id': '2f', 'pid': '2c', 'name': '薪资管理部'},
            { 'id': 'd3', 'pid': 'd2', 'name': 'Java研发部'}
            ]

  
                const map = {}
                const arrNew = []
                arr.forEach(item => {
                    if (!item.children) {
                        item.children = []
                    }
                    map[item.id] = item
                })
                console.log('map1',map);
                console.log('arrNew1',arrNew);
                arr.forEach(item => {
                    const parent = map[item.pid]
                    if (parent) {
                    parent.children.push(item)
                    } else {
                    arrNew.push(item)
                    }
                })
                console.log('map2',map);
                console.log('arrNew2',arrNew);
    </script>
</body>
</html>